Objectives: To characterize the synthesis and processing of heterogeneous nuclear RNA, thought to be the precursor to messenger RNA, in physiologically non-dividing human cells. Points in the metabolic sequence which may be involved in control of normal processing will be sought. The relation between such biochemical controls and modifications in the use of messenger RNA related to growth stimulation will be sought. Comparisons will be made between the functioning of these regulatory steps in normal and neoplastic lymphoid tissues.